Behaviorally trained cats will be used to evaluate the multiple channel scala tympani implant developed by Drs. Michelson and Merzenich. 1. Whether or not the width of the electrical pulses affect perceived loudness will be determined by use of reaction time. 2. Verification of the independence of the various channels will be made with differential conditioning procedures. 3. The limit of the range of repetition rates that affect perceived pitch will be determined by finding the differential frequency threshold (DF) at a number of standard frequencies. The immediate goal of these studies is to provide insights that will be helpful in the design of the electrical package needed to drive the multiple channel cochlear implant. BIBLIOGRAPHIC REFERENCES: Walloch, R.A. and Taylor-Spikes, M.: Auditory thresholds in the guinea pig: A preliminary report of a behavioral techique employing a food reward. Laryngoscope 86:1699-1705, 1976. Walloch, R.A. and Fenwick, J.A.: Problems of guinea pig training and how to solve them. J. Acoust. Soc. Amer. 60 Suppl. 587, 1976.